According to a study carried out at Portsmouth University in 2008, there is a very easy way to tell if someone is lying -- no need for a polygraph test. The study indicated that it is possible to ascertain if someone is lying by observing how frequently they blink. People tend to blink less frequently when they are in the act of lying, and then blink faster than normal after completing the lie.
In the study, 26 volunteers were presented with different scenarios and then asked to answer questions about their activity, requiring some of them to lie. Each volunteer's eye activity was monitored with the use of electrodes. When the results were compared, the researchers found that those who told the truth had maintained the same number of blinks both during and after their answers. The liars, on the other hand, blinked less frequently while they lied and much more afterward.
The researchers believe that the increased mental effort required to tell a lie causes people to blink less as they speak, as they are concentrating on the lie. Other studies have also indicated that as cognitive demand increases, eye blinks decrease.
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